// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
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// modification, are permitted provided that the following conditions
// are met:
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//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
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//    this software without specific prior written permission.
//
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package org.objectweb.asm;

/**
 * A visitor to visit a Java field. The methods of this class must be called in the following order: ( {@code visitAnnotation} | {@code visitTypeAnnotation} | {@code visitAttribute} )* {@code
 * visitEnd}.
 *
 * @author Eric Bruneton
 */
public abstract class FieldVisitor {

	/**
	 * The ASM API version implemented by this visitor. The value of this field must be one of {@link Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
	 */
	protected final int api;

	/** The field visitor to which this visitor must delegate method calls. May be null. */
	protected FieldVisitor fv;

	/**
	 * Constructs a new {@link FieldVisitor}.
	 *
	 * @param api
	 *          the ASM API version implemented by this visitor. Must be one of {@link Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
	 */
	public FieldVisitor(final int api) {
		this(api, null);
	}

	/**
	 * Constructs a new {@link FieldVisitor}.
	 *
	 * @param api
	 *          the ASM API version implemented by this visitor. Must be one of {@link Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
	 * @param fieldVisitor
	 *          the field visitor to which this visitor must delegate method calls. May be null.
	 */
	public FieldVisitor(final int api, final FieldVisitor fieldVisitor) {
		if (api != Opcodes.ASM7 && api != Opcodes.ASM6 && api != Opcodes.ASM5 && api != Opcodes.ASM4) {
			throw new IllegalArgumentException("Unsupported api " + api);
		}
		this.api = api;
		this.fv = fieldVisitor;
	}

	/**
	 * Visits an annotation of the field.
	 *
	 * @param descriptor
	 *          the class descriptor of the annotation class.
	 * @param visible
	 *          {@literal true} if the annotation is visible at runtime.
	 * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not interested in visiting this annotation.
	 */
	public AnnotationVisitor visitAnnotation(final String descriptor, final boolean visible) {
		if (fv != null) {
			return fv.visitAnnotation(descriptor, visible);
		}
		return null;
	}

	/**
	 * Visits an annotation on the type of the field.
	 *
	 * @param typeRef
	 *          a reference to the annotated type. The sort of this type reference must be {@link TypeReference#FIELD}. See {@link TypeReference}.
	 * @param typePath
	 *          the path to the annotated type argument, wildcard bound, array element type, or static inner type within 'typeRef'. May be {@literal null} if the annotation targets 'typeRef' as a whole.
	 * @param descriptor
	 *          the class descriptor of the annotation class.
	 * @param visible
	 *          {@literal true} if the annotation is visible at runtime.
	 * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not interested in visiting this annotation.
	 */
	public AnnotationVisitor visitTypeAnnotation(final int typeRef, final TypePath typePath, final String descriptor,
			final boolean visible) {
		if (api < Opcodes.ASM5) {
			throw new UnsupportedOperationException("This feature requires ASM5");
		}
		if (fv != null) {
			return fv.visitTypeAnnotation(typeRef, typePath, descriptor, visible);
		}
		return null;
	}

	/**
	 * Visits a non standard attribute of the field.
	 *
	 * @param attribute
	 *          an attribute.
	 */
	public void visitAttribute(final Attribute attribute) {
		if (fv != null) {
			fv.visitAttribute(attribute);
		}
	}

	/**
	 * Visits the end of the field. This method, which is the last one to be called, is used to inform the visitor that all the annotations and attributes of the field have been visited.
	 */
	public void visitEnd() {
		if (fv != null) {
			fv.visitEnd();
		}
	}
}
